1. Field of the Invention
The present invention relates to a catheter assembly capable of sanitarily and safely inserting a catheter into a desired position in a human body.
2. Description of Related Art
A catheter assembly is used for introducing a cannula made of a synthetic resin into veins, arteries or a coelom of a patient and injecting a liquid medicine or removing a fluid. When a catheter is inserted into, for example, a vein, there has been conventionally used a method where a piercing needle having an inner diameter larger than an outer diameter of a catheter is first pierced into a vein. A catheter is then guided to a desired position of the vein through a bore (lumen) of the piercing needle and, thereafter, only the catheter is left in the vein by removing the piercing needle from the vein. With this method there is a fear that blood will leak from the skin surface when the piercing needle is removed from the vein or that bacteria will invade the vein or the like when the piercing needle is removed from the vein. Accordingly, the insertion operation of the catheter must be carried out under an aseptic condition.
Therefore, there has been proposed a catheter assembly capable of aseptically inserting a catheter into a human body by guiding the catheter using a sheath without touching the catheter (Japanese Unexamined Patent Publication No. JP-A-2-13471, Japanese Unexamined Patent Publication No. JP-A-2-111376).
The catheter assembly according to Japanese Unexamined Patent Publication No. JP-A-2-13471, is comprised of a cannula, an inserter for slidably holding the cannula and a hub structure attached to a proximal end of the cannula, and is characterized in that a sheath is attached to the hub structure and surrounds the cannula, and the inserter is provided with a sheath stripping means and sheath locking members. After a distal end of the catheter is inserted into a human body along with a needle and the needle is removed from the catheter, the cannula can be inserted further into the body by pulling a tab of the sheath projecting at a distal end thereof. The cannula integrated with the sheath by the hub structure is prevented from retracting by sheath locking members.
Meanwhile, the catheter assembly according to Japanese Unexamined Patent Publication No. JP-A-2-111376, is comprised of a cannula, an inserter for slidably holding the cannula and a hub structure attached to a proximal end of the cannula, and characterized in that a long accommodating tube for accommodating a needle (long piercing member) is provided therein. After a distal end of the catheter is inserted into a human body along with the needle and the needle is removed from the catheter, the needle contaminated with blood can be accommodated in the long accommodating tube.
However, with the a catheter assembly disclosed in Japanese Unexamined Patent Publication No. JP-A-2-13471, there is a danger of exposing the catheter to the outer atmosphere immediately in front of the sheath stripping means when stripping the sheath from the catheter, and insertion failure or breakage of catheter may be caused because the stripping resistance of the sheath from the catheter is large. Further, erroneous insertion may be caused since the resistance in inserting the catheter into a blood vessel is difficult to be perceived by an operator since the stripping resistance of the sheath from the catheter is large. Further, a manipulatively familiar conventional method in which a catheter is inserted into a blood vessel by pushing it is preferably used if safety in inserting the catheter is regarded as important. However, according to the above-described catheter assembly, although the catheter can be inserted into a blood vessel by pushing it if the rigidity of the sheath is increased, the stripping resistance of the sheath is also increased. On the other hand when the rigidity of the sheath is weakened, the sheath cannot be inserted by pushing it since kinking or bending is caused in the sheath.
Meanwhile, according to the catheter assembly of Japanese Unexamined Patent Publication No. JP-A-2-111376, although the needle can be accommodated in the long accommodating tube, if blood is adhered to a wire, the operator can touch the wire with his hand and, accordingly, the danger of blood borne infections still remains.
The present invention has been developed in view of the above-described situation and it is an object of the present invention to provide a catheter assembly capable of sanitarily and safely inserting a catheter into a desired position in a human body by pushing it. Further, it is an object of the present invention to provide a catheter assembly capable of safely disposing of a piercing needle which has been removed after inserting a catheter.